1. Field of the Invention
This invention pertains to a pneumatic seal joint made of elastomer, with improved safety due to an internal septum.
2. Related Art
The practice of utilizing retractable pneumatic joints, which can be inflated under the pressure of a fluid, to achieve a seal between two enclosures, chambers, tanks, or between them and the outside is known. Such joints are used in blowers, radiation chambers, amphibious vehicles, aircraft and spacecraft, for the doors or cofferdams of deactivation pools in nuclear power plants, retreatment shops for irradiated fuel, "white" chambers in the electronic and space industries and sterile rooms in hospitals.
All of these installations utilize, along with metal or concrete parts, or other structural materials, one or more joints providing a seal by inflation with pressurized air or fluid.
Such inflatable joints made of elastomer are described in French Patent No. 2,188,759 corresponding to British Patent Specification No. 1,440,666. In general, this type of joint includes a seal surface, which comes to press against a support, a fixed base, and two lateral walls connecting the seal surface and base.
The major and well-known shortcoming of this type of joint is that upon the appearance of a tear or perforation in one of the walls, the joint becomes defective due to the loss of motor fluid or air. It then becomes completely non-operational due to a retraction from the gap which it filled between the cofferdam or door and the part to be sealed, and it no longer fulfills its sealing function.
A safety device currently in use consists of placing, inside the inflatable joint cavity, an air chamber or impermeable membrane containing air or motor fluid and following all of the movements of the seal surface. Textile insertions, currently utilized in pneumatics, reinforce the walls. Tears or cuts on the outside part of the joint do not necessarily cause the perforation of the walls of the internal membrane. This is the system which is commonly utilized in pneumatic systems in automobiles and motorcycles. But when the wall of the joint is seriously perforated, the internal chamber of the joint is also perforated, since it perfectly lines the inside of the joint wall. The seal is thus destroyed which in most of the aforementioned applications is unacceptable because it can result in consequences which are harmful to the safety of persons and materials.
U.S. Pat. No. 3,359,687 describes an inflatable, expandable joint for aeronautical pressurization systems, including two sealed compartments with corrugated walls which can be inflated individually and which are separated by a partition. The expansion of the joint in service is obtained by the inflation of a single compartment at a high pressure, the other lessinflated compartment remaining retracted. In case the expanded compartment is punctured, the pressure of the other compartment causes it to expand, which allows the expansion of the joint to be maintained. In this operation, the partition separating the two expandable compartments plays a neutral separation role.